1. Field of the Invention
The present invention relates to a lens driving apparatus for electrically driving a lens in the optical axial direction, which is used in a power focusing apparatus, a power zooming apparatus or the like that controls the focus or the angle of view of a camera lens by means of the driving force of a motor.
2. Description of the Related Art
The Japanese Patent Disclosure (KOKAI) No. 63-89826 discloses a power focusing apparatus which has a manually operatable rotational operation member, detects the operational direction, the amount of operation and operating speed of this operation member, and controls the amount of driving, driving speed and driving direction of a camera lens respectively based on the detected amount of operation, operating speed and operational direction. Conventionally, a DC motor is used to drive such a camera lens. Since a DC motor has a low response speed and a large inertia, however, there is a demand for a new motor which has a small inertia and a good response characteristic and is suitable for driving a camera lens.
According to the conventional controlling method which detects the operational direction, the amount of operation and the operating speed of a rotational operation member and controls a motor in accordance with the detected data, however, if a motor having a good response characteristic such as an ultrasonic motor is used, it would respond too finely even to a slight change in operation of the rotational operation member. Although the motor can respond to manual operation with a high fidelity, the lens would move awkwardly if hand movement is awkward. The resultant operability is not particularly good. This also applies to a power zooming apparatus.